Sheet materials such as drywall are commonly used for wall cladding in the construction of buildings and houses. These sheet materials are usually supplied in selected sizes, such as 4 feet .times. 8 feet. When installing these sheets it is often necessary to cut a circle, and remove the disk which is thus formed, to install a fixture, such as, an inset lighting fixture. Similarly, it is sometimes necessary to cut a circular hole in drywall which has already been installed.
A variety of tools is commonly used to cut circular holes in drywall. For example, hand tools, such as, chisels and keyhole saws are used for this purpose. Power tools, such as, drill-powered hole saws and sabre saws are also utilized to cut circular holes in drywall. The above tools have well known disadvantages. For example, while a power hole saw usually cuts a neat circle, it generates a considerable amount of gypsum dust which is generally bothersome to persons who are near the hole cutting site. Also, the large diameter holes saws which am needed for large circular holes generate torque during the use of the hole saw which makes it a difficult and somewhat hazardous operation for the user of the tool. Sabre saws also generate a considerable amount of gypsum dust and these tools have the additional disadvantage that the edges of the circular holes are rather jagged which may require an additional finishing operation.
The above mentioned hand tools require more time for cutting a circular hole than power tools and they generally do not result in neat cuts thus often requiring an additional finishing operation. Also, it is difficult to make an accurate circular hole using these hand tools.
Circular cutters for such diverse sheet materials as paper, cork, rubber and glass are well known. Typically, these cutters include (1) a cutting member for cutting or scribing the sheet material, (2) a pivoting member for temporarily affixing the cutter to the center of the circle and (3) a beam or arm connecting the cutting member and the pivoting member. Generally, a marked distance scale is provided on the beam. These types of cutters are commonly known as circle cutters, circle scribers, curved line scribers and beam compasses.
For example, U.S. Pat. Nos. 5,235,754 (Sirois, 1993), 5,065,517 (Markes, 1991) and 2,943,392 (Attridge, 1960) disclose beam compass types of circle cutters each having a cutting member, a pivoting member and a beam. However, these circle cutters do not provide an optimal design for cutting drywall because the performance of these tools is likely to be adversely affected by gypsum dust.
For example, the '754 patent teaches a compass holder which slides on a beam. Gypsum dust caking on the compass holder may interfere with the sliding movement of the compass holder thus resulting in either inaccurate circle cuts or in down-time which is necessary to clean the tool. The '517 patent teaches a cutting block which is slideably received by a slot and is held in position by a thumbscrew, or in another embodiment by a spring-biased detent ball. The slideable positioning of the thumbscrew and the spring-biased detent ball are likely to be adversely affected by gypsum dust. The '392 patent teaches a pivot assembly which is slideably received in exposed slots in the beam thus resulting in a tool which does not have an optimal design for use in a gypsum dust environment.
Gypsum dust is usually present wherever drywall is being installed or cut. Gypsum dust is known to cake on hard surfaces. This dust is abrasive and is likely to ultimately wear down surfaces which make a sliding or a screw contact.
Accordingly, the need exists for a drywall circle cutter having improved ease of use while being less affected by abrasive dust than currently known circle cutters.